This project will use intracellular recording and HRP injections into single physiologically identified LGNd neurons in kittens. The relationship between cellular structure and function in the developing postnatal, brain will be obtained. In addition, new information on development of the synaptic physiology of the central visual pathway will be gained. This will include the nature and timing of synaptic inputs from cortex and retina. The membrane properties of kitten LGNd cells will also be measured to determine to what extent these parameters influence development of adult-like physiological properties. Experiments will concentrate on the developing A laminae of LGN. However, the other subdivisions (MIN, PGN, and C laminae) will be studied, also. In addition to the light microscope analysis of physiologically identified neurons, the synaptology of some cells will be further analyzed at the ultrastuctural level with electron microscopy. This project should produce a framework of the normal relationship of neuronal function and structure in the developing visual system. Later studies on how this relationship is altered, during abnormal visual development can be compared to the normal developmental sequence.